This invention relates to a vector control method for a permanent magnet motor operated in the region of weak magnetic field.
A conventional example of the vector control for a permanent magnet motor operated in the region of weak magnetic field is disclosed in the Japanese patent document, JP-A-08-182398, wherein the d-axis current command value is tabulated and the control of the d- and q-axis currents is performed on the basis of the P-operation (proportional operation). Another conventional example is disclosed in the Japanese patent document, JP-2002-95300, wherein the motor terminal voltage is derived from the control section for the d- and q-axis currents and the d-axis current command value is obtained through the PI (proportional and integrating) operation on the basis of the difference between the terminal voltage and the terminal voltage command value.